Combating insects



Patented. Oct. 25, 1938 COMBATING INSECTS Karl Brodersen and'Matthias Quaedvlieg, Dessau in Anhalt,

Germany, assignors to Winthrop Chemical Company, Inc., New York, N. Y., a corporation of New York No Drawing. Application June 23, 1936, Serial No. 86,821. In Germany November v30, 1932 9 Claims.

Our present invention relates to new improved .nsecticides and to a new process of destroying pests. It is a continuation-impart of our copending application Serial No. 694,685, filed Octo- 5 her 21, 1933. v

I For destroying pests of all kinds a large number of organic compounds has been'used, for instance ethers, esters, alkylene-oxides, aldehydes. ketones, ac'id amides, amines, sulfides or mercap- 10 tans.

action in gaseous form and for this purpose apparatus of one sort or another has been necessary in particular evaporators or cloud-producers, so that the mere introduction of the destructive ll agent into the room to be treated does not sufllce.

In the case of very volatile agents of this kind,

dimculties arise during transport, particularly in hot climates, and in these cases the agents have to be supplied in steel bottles. This'in itself is a 20 disadvantage, because the liquefied substance absorbs much heat during its volatilization, so that the speed of evaporation diminishes and a con-- stant rate of ,evaporation of the agent presents difllculty. The problem to be solved is how to 25 obtain rapid and complete evaporation in order that the eifective concentration of the vaporized agent in the atmosphere may be achieved as quickly as possible.

The present invention overcomes the several 80 difllculties inherent to the use of agents of this kind by using aliphatic esters of formic acid in the form of an addition coinpound with an inorganic salt. Such compounds decompose with spontaneous heating and yield the destructive 86 agent in the i'orrn of vapor byactlon of water. This decomposition and evolution of the vapor may be secured by adding water to the addition compound; on the other hand, the atmospheric moisture, moisture in the soil or moisture adher- 40 ing to the goods to be treated, may be used for liberating the active agent from the addition 1 compoimd.

Addition compounds of the kind in question are, for instance, those of methyl formate, ethyl 45 inmate, propyl formate, butyl iormate, or other esters of formic acid having a boiling point not higher than about 150 C. and having a low vapor tension at ordinary temperature, with magnesium chloride or calcium chloride. These addition 50 compounds are obtainable easily and in good yield by treatment of the anhydrous salt (magnesium or calcium chloride) with the esters of formic acid in question. Thus, for instance, anhydrous magnesium chloride in a finely pulverized state 55 and beingiree from hydroxy chloride as far as These compounds'have been brought into possible, is treated in a ball mill with vaporized methyl formate under exclusion of water or moisture.- The temperature which slightly raises during the formation of the double compound, is kept at about 30 to 35. C. and this treatment is continued until about 2 mols of the ester are taken up by the magnesium chloride. It corresponds to the formula MgCl2-2HCOOCH3. The addition compounds of other formic esters with magnesium chloride or calcium chloride respectively, are produced in an analogous manner. They form crystallized compounds and may, in contrast with the liquid insecticides, be packed in simple sheet metal. boxes, in which they can be exported and preserved for practically an unlimited time. They may be used in definite doses more easily than is possible with the liquid or gaseous agents.

It is advantageous in some circumstances to use the double compound in admixture with a neutralizing agent, such as chalkv or magnesia; or with a diluent, such as talc or bolus. In particular cases, for example-for destroying underground pests, manurial constituents may also. be added. Other known solid agents having an insecticidal or bactericidal action, such as para- 5 dichlorobenzene, naphthalene, camphor or para.- formaldehyde, may be used in conjunction with the addition compound according to this invention.

These agents can be used, for example, for destroying weevil in barns, elevators or silos. Also'the pests in foods and fodders, for instance the peaand lentil-beetles, 'or in leguminous vege-' tables. The process is not limited to its application to corn or the like it may be applied equally well for destroying vermin in skins, clothing, rags or the like; also for exterminating mice or n oles from their burrows in agricultural soil.

The atmospheric moisture suiflces to decompose the addition compound of the formic acid ester and the said inorganic salts so as to volatilize the former in the enclosed space. For example, for securing along sustained concentration of vapor of the destroying agent in a small closed chamher, such as a dwelling room, a cupboard or a museum case, the addition compound to be used may be placed in an open dish so that the natural or, if desired, artificially increased "content of moisture in the air may decompose the compound with evaporation of the destroying agent.

In the case of destroying pests in loosely lying material, for example in wheat or pulse, even in very large stores it 'suflices to distribute the addition compound in the goods to be treated. The

moisture adhering to the goods sumces to liberate the eflfective agent from the compound.

The following examples illustrate the invention:

Example 1.A bin of about 1 cubic meter capacity is charged with 15 centners of corn strong-- ly infected with weevil. At the same time 600 to 800 grams of a compound of calcium chloride -with methyl formate having a content of about 40 to per cent. of the latter is intermingled with the corn. After 24 hours every weevil is found to have been ldlled. A

Example 2.-- parts by weight of an addi tion compound made from methyl formate and anhydrous magnesium chloride and containing about 50 per cent. of methyl formate is covered .with 100 to 200 parts of water. This mixture -.a boiling point not higher than C. with an anhydrous alkaline earth metal chloride of the.

group consisting of magnesium and calcium chloride, which double compound is decomposed by the action of water or'moisture.

'2. A solid insecticide comprising an addition compound of methylformate with an anhydrous alkaline earth metal chloride of the group consisting of magnesium chloride and calcium chloride, which double compound is decomposed by the action of water'Eor moisture.

3. A solid; insecticide comprising the addition compound of methylformate with anhydrous magnesium chloride corresponding to the formula MgCh-ZHCOOCHa, which double compound is decomposed by the action of water or moisture.

4. A solid insecticide comprising the addition compound of methylformate with anhydrous calcium chloride corresponding to the formula CaCiz-ZHCOOCHs, which double compound is decomposed by the action of water or moisture.

5. The process for combating pests in enclosed spaces which comprises introducing into the closed space a preparation containing an addition compound of an alkyl ester 01' formic acid having a boiling point not higher than 150 C. with an anhydrous alkaline earth metal chloride of the group consisting of magnesium chloride and calcium chloride and acting upon this addition compound with water or moisture.

6. The process for combating pests in enclosed spaces which comprises introducing into the closed space a preparation containing an addition compound of methylformate with an anhydrous magnesium chloride and acting upon this addition compound with water or moisture.

7. The process for combating pests in enclosed spaces which comprises introducing into the closed space the compound of the formula MgCh-ZHCOOCH: and acting upon this addition compound with water or moisture. I

8. The process for combating pests in enclosed'spaces which comprises introducing into the closed space the compound of the formula CaClz-2HCQOCH: and. acting upon this addition .compound with water or moisture.

9. Thefprocess for combating pests in corn which comprises mixing the corn having its natural moisture with'a preparation containing an 

